1. Field of the Invention
The invention is a device for measuring the respiration rate of a patent, in particular, to a portable hand held device for making such measurements.
2. Description of Related Art
There are two major types of devices that measure the respiration rate of a patient; one type measures the expansion and contraction of the chest cavity and the other type measures the respiration by sensing the airflow into and out of the lungs during inhaling and exhaling. A description of the former type can be found in IBM Technical Disclosure Bulletin, Vol 6, No. 6, November 1963 wherein a respiration transducer by G. R. Willis is disclosed. This respiration transducer comprises a chest band having a first end attached to a housing and a second end attached to a mirror movably mounted within the housing. The Mirror is biased toward the first end of the band by a spring mounted within the housing. A lamp and light sensor are mounted within the housing, separated by a light barrier. As the patient breathes, the mirror is moved away and toward the lamp and the sensor; thus creating a series of pulses that can be counted and which correspond to the breathing rate. In U.S. Pat. No. 5,107,846, "Displacement Detector Device and Method" by D. Atlas a similar system. Here the mirror is moved back and forth across the end of a optical fiber. A LED/photodiode transmits and receives light transmitted down a optical fiber and reflected off the mirror. The interruption of the signal as the mirror is moved back and forth under the optical fiber as the patient breaths in and out providing an indication of the respiration rate. While these devices will record respiration rates, they have the disadvantage of requiring that they be attached about the patient's chest. This is a time consuming operation and, in some cases, particularly if the patient can not be moved, they can not be used at all.
In U.S. Pat. No. 4,981,139, "Vital Signs Monitoring And Communication System by R. L. Pfohl a sound sensor attached to the chest is used to monitor the respiration rate. Here the patient need not be moved to achieve attachment of the device; however, it is not a self contained unit. Additionally, as with the Willis and Atlas devices they depend on significant movement of the chest wall to produce a signal. If the respiration is shallow meaningful readings may not be obtainable. It is also difficult to differentiate body movement from respiration if the patient is in motion.
An example of the second type can be found in U.S. Pat. No. 3,611,801, Respiration Monitor" by R. J. Fagot, et al. In the Fagot, et al device the patient breaths through a tube with connects directs to a housing having a microphone mounted therein. The sound of the air rushing passed the microphone is recorded as electrical pulses that can be counted. The problem with this device is that it requires sophisticated electronic circuits such as pulse shapers and, thus is unnecessarily expensive.
In the devices disclosed in U.S. Pat. Nos. 5,137,026, "Personal Spirometer" by C. K. Waterson, et al. and 4,984,158, "Metered Dose Inhaler, Biofeedback Training And Evaluation System" by E. Hillsman the patient breaths into a tube connected to a housing having an orifice mounted therein. The respiration rate is determined by measuring the pressure drop across an orifice by a differential pressure transducer. Here again sophisticated electronic circuitry is necessary in order to eliminate spurious signals and provide accuracy.
Thus, it is a primary object of the invention to provide a portable respiration rate measuring device.
It is another primary object of the invention to provide a portable respiration rate measuring device that is inexpensive to manufacture.
It is a further object of the invention to provide a portable respiration rate measuring device that is extremely accurate.